trichostatin-a and Leukemia--T-Cell

Histone deacetylase is overexpressed in a variety of cancers and is closely correlated with oncogenic factors. A histone-deacetylase inhibitor, trichostatin A (TSA), has been shown to induce apoptosis in many cancer cells at submicromolar concentrations. However, the mechanism remains unknown. This study was to investigate the underlying mechanism of trichostatin A on apoptosis of Molt-4 cells by characterizing the global gene expression profiles before and after TSA treatment.. PI single-labeled flow cytometry, MTT and DNA ladder were used to observe the effect of TSA on apoptosis of MOLT-4 cells and normal human peripheral blood mononuclear cells (PBMC). Microarray and reverse transcription-polymerase chain reaction (RT-PCR) and Western blot were used to detect the differentially expressed genes of Molt-4 cells after incubation with TSA.. TSA could induce apoptosis in Molt-4 cells in a dose and time-dependent manner. Besides, the dose of TSA within the time duration which could induce significant apoptosis in Molt-4 cells did not demonstrate apparent cytotoxicity to PBMCs. After incubation with TSA for 9 hours, 313 genes were detected down-regulated by microarray. Proteins encoded by these genes included signal transduction molecules, transcription factors, enzymes etc., which were involved in the regulation of cell growth, differentiation and survival. STAT5A, MYC and ikaros were down-regulated by 80.4%, 77.3% and 83.1%, respectively. The changes of the three genes were confirmed by RT-PCR and the changes of STAT5A and MYC were further confirmed by Western blot.. The inhibition of cell growth and induction of apoptosis by TSA in Molt-4 cells may be due to the changes of pro-proliferation genes and anti-apoptosis genes.

Topics: Apoptosis; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Flow Cytometry; Gene Expression Profiling; Histone Deacetylase Inhibitors; Histone Deacetylases; Humans; Hydroxamic Acids; Ikaros Transcription Factor; Leukemia, T-Cell; Leukocytes, Mononuclear; Protein Array Analysis; Proto-Oncogene Proteins c-myc; RNA, Messenger; STAT5 Transcription Factor; Tumor Suppressor Proteins

In thymocytes butyrate and trichostatin A are unable to augment dexamethasone-induced apoptosis. In cultured rat thymocytes the extent of apoptosis induced by dexamethasone alone did not increase by addition of 0.1 - 10 mM butyrate. Even more pronounced was the non-additive interrelationship between dexamethasone and trichostatin A, as trichostatin A-induced apoptosis was not only blocked by the presence of dexamethasone but dexamethasone-induced apoptosis was also partially inhibited in the presence of 0.1 - 0.5 microM trichostatin A. The fact that the non-additive relationship with dexamethasone for apoptosis induction was observed with both histone deacetylase inhibitors suggests that in thymocytes this phenomenon is related to histone acetylation. In contrast to this, in the human T cell-derived leukemia cell line CEM-C7H2, dexamethasone did not block butyrate- or trichostatin A-induced apoptosis; moreover, butyrate, in the concentration range of 0.1 - 1 mM, had a marked synergistic effect on dexamethasone-induced apoptosis. This synergism, however, was not mimicked by trichostatin A, indicating that the effect is not related to histone acetylation but rather due to a pleiotropic effect of butyrate. Furthermore, in CEM-C7H2 cells, at higher concentrations of butyrate (5 - 10 mM) or trichostatin A (0.4 - 0.8 microM), there was a minor but reproducible antagonistic effect of dexamethasone on apoptosis induced by each of the two histone deacetylase inhibitors, suggesting that this antagonistic effect too, is related to histone hyperacetylation.

Topics: Animals; Apoptosis; Butyrates; Cells, Cultured; Dexamethasone; Drug Interactions; Drug Synergism; Humans; Hydroxamic Acids; Leukemia, T-Cell; Rats; T-Lymphocytes; Tumor Cells, Cultured